The present disclosure is directed to a drill bit construction and more particularly to a drill bit construction which includes or incorporates a bifurcated body which supports two cutting faces. It is constructed at the end of a stem which is suitably connected with a chuck and drill motor which especially finds use in drilling long holes in shaft mines for anchoring mine support timbers. When a mine is extended into an overburden, shoring is required to support the overburden and to prevent collapse of the mine roof on people in the mine. This is accomplished by shoring up corridors in the mine with vertical columns connected with roof beams. The shoring is anchored to the overburden. This is typically done by drilling numerous small holes up to about 5 feet in depth into the overburden. The holes need only be about 1 or 3 inches in diameter to provide adequate connection for an anchor rod which is positioned in the drilled hole. The anchor rod connects to the shoring to assure proper supportive interconnection.
The interconnection which is necessary is important to the safety of the mine. The anchor rods are normally positioned in the holes of perhaps 1 to 3 inches in diameter by bonding the rods in the holes. This requires drilling of hundreds or typically thousands of holes for a given situation. To drill all of the holes, it is necessary to use a drill bit which is capable of drill through rock. The bifurcated bit structure of this disclosure is well able to provide hundreds of drilled holes thereby extending the life of the device substantially in comparison with drill bits now in vogue. In one aspect, the drill bit of the present disclosure is a device which is provided with duplicate spaced cutters. In this particular embodiment, the cutter is supported on a tool steel body. The body is formed of a hard steel, one choice being 4340 steel. The body supports two cutting inserts. The inserts are attached by brazing. In addition to that, the cutters are faced with a planar coating of polycrystalline diamond compact PDC hereinafter) which is bonded by brazing or the like. This reinforces the insert face and enables the bifurcated bit to last substantially longer.
The drill bit body is constructed with a sloping face having a semi-cylindrical mounting surface in the central portion of the face. The curving portion serves as a lock to receive an insert which is brazed to it. The insert, formed of PDC, is attached on the semi-cylindrical surface in conjunction with the shoulder. This provides locking multiple surfaces at angled positions to assure that the PDC insert is held throughout the life of the device. This safely anchors the PDC insert. In addition to that, it enables the PDC to be presented at drilled hole surfaces which enable enhanced contact with the hole during drilling. The leading face of the PDC insert is overlaid with a thin layer of diamond which is brazed or otherwise bonded to it. That enhances the protection of the bifurcated cutting tool of the present disclosure.
In one aspect of this equipment, the insert is formed of PDC which is cut from a circular blank. Furthermore, this blank is in the form of a PDC circular blank or segments thereof having, requisite thickness. This segment of material defining the faced cutter element thus forms two PDC inserts from a single PDC disk of cutting material. When cut, the two parts are readily made for the two cutter faces.